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hydro-static press cracking studies

The picture shows a Hydro-static Press for forming ceramic components (in this case "funnels"). The Boot and Mandrel, (the brown cone shape below the open breech) contained ceramic powder that was pressed into the solid shape under hydro-static pressure.

The boot itself was molded from Urethane and was approximately 1.5" thick. The pressure could be as high as 30,000 psi but typically was only between 10,000 and 15,000 psi. Cracking was a chronic problem, resulting in poor yields of the pre-fired fragile parts.

The extremely high pressures made it difficult to analyze the nature of the cracking mechanism. A series of tests were conducted to understand the interaction of the thick urethane "boot" and the green ceramic parts. High speed images of the decompression curve were captured with a high pressure transducer.

The nature of the cracking mechanism was discovered and changes were made to the process to reduce the cracking problems.